The manufacture of two piece containers such as metallic beverage cans by the draw and iron process is widely practiced. According to this known technique, sheet metal coil stock is fed into a machine called a cupper. There, the sheet is blanked into round discs of metal. These discs are cut in a close pattern, with the rows nested with each other to the extent possible. However, a web of metal remains behind after the discs are removed, and this web constitutes scrap. The cupper then processes the discs so formed into shallow cups, which are substantially wider in diameter than the finished can body. The scrap may be disposed of an various ways, including reprocessing it into additional sheet stock.
The cups are further processed in a bodymaker machine. Here, a punch pushes each cup through a series of dies. The first die is a redraw die that reduces the diameter of the cup to the eventual diameter of the finished can body. Subsequent dies draw and iron the side walls of the can body, extending them to increased height, generally greater than the finished height of the can. The open end of the can body is quite irregular after bodymaking and, thus, the can body is further processed in a trimming machine. There, the irregular open end is trimmed off, leaving behind a can body of standard dimensions and finished open end edge. The trimmer leaves another scrap, which can be reprocessed to form additional stock.
After trimming, often the can body is further processed by printing a decoration on the outer surface wall and necking-in the open end. With or without necking-in, the can body then is flanged at the open end. At this point, the body may be filled with its intended contents. Once filled, the body is closed by applying a lid over the flanged end and seaming the lid and flanged end.
Many patents disclose details of the draw and iron process of forming container bodies. In all known processes, the blanking step generates scrap between blanks. A recent article, K. Forth, New Company Has Been Around For Can Manufacturers, CanTech International, October/November 1994, describes a process for cutting blanks having the shape of a modified hexagon. The process reduces the amount of scrap by allowing a closer blanking pattern. However, scrap still is generated between blanks.
Several patents disclose techniques of saving metal in forming lids, also known as can ends. Of note is U.S. Pat. No. 4,244,315 to Klein, which proposes that lids might be blanked from square blanks, from scrolled strips of metal, or from wide sheet stock, in each case employing a preliminary closure forming step that draws metal from outside the border of the lid. The pattern in which the lids are arranged is a staggered, hexagonal, honeycomb arrangement, intended to produce a maximum number of lids from a given amount of sheet metal. However, it is notable that the lids, when cut from the sheet stock, are circular, leaving behind a substantial scrap at the interstices of the pattern. Other notable art is found in U.S. Pat. No. 4,106,422 to Buhrke, which proposes that lids be formed while remaining integral with the coil stock. Various processing is applied to the lids to finish them to the maximum extent possible before the lids are cut from the stock. Thus, prior to being finally cut, the lids are carried in the stock in a local area of metal having plane geometric outlines. However, when finally cut, the lids are circular and leave behind scrap.
It would be desirable to form container bodies according to generally known techniques of the draw and iron process, but with far less scrap then is presently produced. Such an advancement would improve the efficiency of container manufacturing by producing an increased number of container bodies from a given amount of metal Similarly, this improvement could eliminate a substantial amount of metal reprocessing that currently is required due to the large generation of scrap in all known can body forming processes.
Similarly, it would be desirable to form lids with reduced scrap.
To achieve the foregoing and other objects and in accordance with the purpose of the present invention, as embodied and broadly described herein, the product and method of manufacture of this invention may comprise the following.